In the initial progression of dental caries, certain bacteria in the oral cavity metabolize sugar to make organic acids as a product. Some of these organic acids include formic acid, succinic acid, butyric acid, proprionic acid, acetic acid and lactic acid. It is the proximity of this acidogenic bacteria to the tooth surface and the contact of the acid with the surface that eventually causes a breakdown of enamel or demineralization. The frequency of this production and the longer the contact with the enamel, the greater degree of demineralization for the eventual progression to a caries lesion. Lactic acid in particular is increased after plaque is exposed to a sucrose challenge and has been shown to be one of the more detrimental acids produced for the demineralization of the tooth.
Not all bacteria in the oral cavity are cariogenic or otherwise damaging, however. The type of bioflora in the mouth plays a significant role in the development of cavities and in oral health generally. For example, arginine and other basic amino acids have been proposed for use in oral care and are believed to have significant benefits in combating cavity formation and tooth sensitivity. It has been hypothesized that a significant factor in the beneficial effect of arginine is that arginine and other basic amino acids can be metabolized by certain types of bacteria, e.g., S. sanguis, which are not cariogenic and which compete with cariogenic bacteria such as S. mutans, for position on the teeth and in the oral cavity. The arginolytic bacteria can use arginine and other basic amino acids to produce ammonia, thereby raising the pH of their environment, while cariogenic bacteria metabolize sugar to produce lactic acid, which tends to lower the plaque pH and demineralize the teeth, ultimately leading to cavities.
In developing new compositions and methods for oral care, it may be desirable to focus on inhibiting, destroying or discouraging particularly those bacteria that cause the damage, rather than simply using methods that kill all bacteria, and/or to focus on methods that neutralize or disperse the damaging acids.
Capillary electrophoresis, e.g. capillary zone electrophoresis, separates ionic species by charge, frictional forces and hydrodynamic radius. In traditional electrophoresis, electrically charged analytes move in a conductive liquid medium under the influence of an electric field. Capillary electrophoresis separates ions based on their size to charge ratio in the interior of a small capillary filled with an electrolyte.
Capillary electrophoresis has been used to measure acids in plaque. See, e.g., Damen J. J. M., et al. Caries Research (2002) 36: 53-57. WO 2009/100262 (incorporated herein by reference) discloses monitoring of both acid and ammonia in plaque, but the methods for measuring ammonia, adapted from a plasma diagnostic kit, are time consuming, taking about a week to complete. Also this method is not suitable for high-throughput use.
In studying plaque formation and tooth decay, and in developing new compositions and methods for oral care, therefore, it would be useful to have a simple, fast, easy-to-use method to measure ammonia production and optionally also acidification of plaque, which can allow one to assess the presence and activity of beneficial and optionally also cariogenic bacteria in the plaque, as well as to assess the disease state of the patient, and the effectiveness of oral care compositions and methods. It would be moreover be useful to have more efficient ways to monitor the type of bioflora in the mouth, e.g., to determine the optimal treatment and to monitor the effectiveness of treatment.